Adjustable electrical trench



March 1, 1966 F. w. FORK ADJUSTABLE ELECTRICAL TRENCH Filed June 27, 1961 INVENTOR.

FP4/V/f 44 1 01? BY A/ 6 Q A 770/F/VE) United States Patent 3,237 ,356 ADJUSTABLE ELECTRICAL TRENQH Frank W. Fork, Pittsburgh, Pa., assignor to H. H. Robertson Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed June 27, 1961, Ser. No. 119,977 16 Claims. (Cl. 52-220) This invention relates to an electrical trench assembly. More particularly this invention relates to an electrical trench which can be utilized in conjunction with metal cellular flooring for building construction as well as in conjunction with underfloor electrical distribution facilities associated with reinforced concrete flooring buildings.

The provision of underfloor electrical raceways in modern buildings has become standard construction. The use of metal cellular floor for this purpose is well known in the art. See US. Patent 2,445,197. Provision of trenches and raceways in poured concrete flooring similarly is well known in the art. As the electrical usage in modern buildings has increased, the need for greater electrical carrying capacity has become apparent. Similarly the changeable character of a buildings usage emphasizes the need for increased accessibility to electrical carrying channels to accommodate frequent alterations in the electrical utilization.

According to a preferred embodiment of this invention, a readily accessible electrical trench is provided for use in cooperation with metal cellular flooring.

The development of reinforced concrete flooring which does not employ metal cellular flooring as a support has generated a need for electrical wire carrying trenches within such concrete flooring. The present electrical trench can be installed in reinforced concrete flooring where cooperation is not required with metal cellular flooring.

The present electrical trench is convenient to assemble and provides convenient access for maintenance and adjustment throughout the life of a building in which it is installed. The present electrical trench can be used in cooperation with metal cellular flooring and also can be used independently in poured reinforced concrete flooring. The present electrical trench has a unique vertical adjustabili-ty and screed leveling feature. A rugged construction characterizes the present electrical trench. The component elements of the present electrical trench can be adapted to accommodate trenches of varying size and various floor thicknesses. The present electrical trench, in addition, can be leveled entirely from above through leveling means. The present electrical trench may be factory-assembled tor immediate installation in a building site.

One problem which has always proved troublesome to building constructors is the inherent variation in concrete thickness which appears in poured concrete flooring. That is, the concrete fill is thicker between supporting beams than in regions overlying supporting beams. The weight of the unsupported concrete in the spans between supporting beams creates an inherent sag and a corresponding increased concrete thickness. Horizontal surface alignment of trench elements has been difficult to accomplish. Frequently the differential thickness of concrete is one inch and more. A differential thickness of at least one-half inch is common-place.

Horizontal alignment of the present electrical trench can be readily accomplished. A further problem which has confronted building constructors concerns decorative floor coverings (linoleum, asphalt tile, rubber tile, ceram- 3,237,356 Patented Mar. 1, 1966 ie tile and the like) which is applied over the upper surface of the poured concrete floors. Divider strips are desirable between the actual floor area and the cover of the electrical trench. According to this invention, a divider strip is provided which is flush with the level of concrete during the actual construction stages of the building, i.e., corresponds with the screed line, yet, thereafter, the divider strip is above the screed line so as to be at the level of the decorative floor covering.

The present electrical trench moreover can be completely assembled in suitable lengths at the factory so that no loose spare parts or auxiliaries are required for installation or final assembly.

An object of the present invention is to provide a versatile electrical trench comprising a unique assembly of component elements.

A further object of this invention is to provide an electrical trench which can be leveled readily without departing from an overall rugged construction.

Another object of this invention is to provide an electrical trench which can be assembled in various dimensions from common elements.

A still further object of this invention is to provide an electrical trench having an interior passageway which is readily accessible throughout the life of the building in which it is installed.

Another object of this invention is to provide an electrical trench comprised of elements which can accommodate decorative floor finishing materials by providing a suitable divider strip which is maintained below the concrete screed line during actual construction yet is above the screed line.

A further object of this invention is to provide an electrical trench which may be adjusted from above for surface alignment from a factory assembled condition.

These and other objects and advantages of the present invention will become apparent from the following detailed description by reference to the accompanying drawings in which:

FIGURE 1 is a fragmentary plan view of the present electrical trench assembled above conventional metal cellular flooring;

FIGURE 2 is a fragmentary cross-section view of the present electrical trench taken along the line 22 of FIGURE 1 and showing especially the leveling screws of this trench;

FIGURE 3 likewise is a fragmentary cross-section view of the present electrical trench taken along the line 22 of FIGURE 1 and showing the leveling screws in an elevated position and further showing the alternate positioning of a spacer channel to accommodate a decorative floor covering;

FIGURE 4 is a fragmentary cross-section view of the present electrical trench taken along the line 4-4 to illustrate cover fastening screws;

FIGURE 5 is an exploded perspective illustration of the elements which comprise the present electrical trench;

' and FIGURE 6 is a fragmentary perspective illustration of an alternative embodiment of the longitudinal channel.

The present electrical trench is designated generally by the numeral 10 in FIGURE 1 where the trench 10 is shown in .a preferred environment in association with metal cellular flooring 11. The metal cellular flooring 11 serves as conduits for electrical cables 12. The electrical trench 10 serves as a major feeding conduit for the electrical cables which pass through corresponding openings in the base of the trench and the upper surfaces 13 of the metal cellular flooring. Concrete 14 is poured above the upper surfaces 13 of the metal cellular flooring 11 to serve as a rigid floor for the resulting building. Norrnally a decorative floor covering 15 (FIGURE 3) is pro vided above the concrete 14, for example, linoleum, asphalt tile, rubber tile, ceramic tile and the like.

The present electrical trench 10 comprises an essentially U-shaped channel 16, a pair of longitudinal channels 17, a pair of Z-shaped linear spacer strips 18, cover plates 19, leveling screws and fastening screws 21.

The U-shaped channel 16 has a horizontal web 22 or base, which rests upon the upper surfaces 13 of the metal cellular flooring 11. Vertical leg members 23 extend from the edges of the web 22 and terminate in generally horizontal flanges 24. A plurality of spaced threaded openings 25 is provided in the horizontal flanges 24 for threadedly receiving leveling screws 20. The U-shaped channel 16 preferably is formed from metal such as steel sheet of thickness from about 12 gauge to about 24 gauge.

In order to provide access from the present electrical trench into the wire carrying cells of the cellular flooring 11, it is necessary to provide an opening through the web 22 and the upper surface 13 of the cellular flooring 11. Conveniently this can be accomplished by cutting holes 50 with a hole saw through the two metal sheets. Normally the perimeter of the holes 50 is lined with a soft metal grommet 51 to prevent any rough edges from abrading the insulation covering of electrical cables which are passed through the holes 50.

The longitudinal channel 17 or screed bar comprises a vertical web 26, an upper horizontal leg 27, a lower horizontal leg 28, a vertical upward flange 29 and a vertical depending flange 30. The vertical web 26 and the two horizontal legs 27, 28 comprise the body portion of the longitudinal channel 17. If desired, the body portion could be fabricated as a solid element, as shown in FIG- URE 6 where the alternative longitudinal screed bar 17 has a body portion 31 with an inner face 32 and vertical flanges 29',

The horizontal legs 27, 28 have spaced clearance openings 33 corresponding with the spaced threaded openings 25 of the horizontal flange 24. Leveling screws 20 extend downwardly through the clearance openings 33. A plurality of spaced threaded openings 34 also is provided in the upper leg 27 for threadedly receiving fastening screws 21. An outwardly extended horizontal tongue 35 is provided at the upper end of the vertical upward flange 29.

The leveling screws 20 have a threaded shaft 36 and a slotted head portion 37 of greater diameter than the shaft 36. The head portion 37 has a slot for receiving a screw driver tip or similar screw turning implement.

It will be observed that the lower leg 28 of the longitudinal channel 17 lies on the generally horizontal flange 24. (FIGURES 2 and 4). The longitudinal channels 17 preferably are extruded from aluminum.

The linear spacer strips 18 have a central portion 38 and two vertical lips 39, 40. The vertical lip 39 is longer than the vertical lip 40. The vertical lip 40 terminates flush with the upper surface of the horizontal tongue 35 when the central portion 38 of the linear spacer strip 18 rests on the upper surface of the upper horizontal leg 27. The central portion 38 of the linear spacer strip 18 has the same length as the upper horizontal leg 27 The vertical lip 39 (FIGURES 2 and 4) abuts the vertical web 26.

A pair of recessed gasket-receiving grooves 41 is provided in diagonally opposed ends of the central portion 38. A suitable bead 42 of resilient gasketing material is provided in at least one of the gasket-receiving grooves 41. Spaced clearance holes 43, 44 are provided in the central portion '38 of the spacer strip 18 corresponding to the clearance openings 33 and the threaded openings 34 of the longitudinal channels 17. The spacer strips 18 preferably are extruded from aluminum.

The cover plates 19 are generally rectangular having side edges 45 and abutting end edges 46. The side edges 45 are tightly fitted between the upper one of the vertical lips 39, 40 and rest upon the upper surface of the central portion 38. A plurality of screw-receiving openings 47 is provided adjacent to the side edges 45 to receive the fastening screws 21 which extend through the openings 47, through the openings 43 of the spacer strip 18 and are threadedly engaged in the threaded openings 34 of the longitudinal channels 17. When the fastening screws 21 are installed, the cover plates 19, spacer strips 18 and longitudinal channels 17 are rigidly secured as a subassembly. The cover plates 19 preferably are formed from steel plate of about one-quarter inch thickness.

A plurality of spaced access openings 48 is provided adjacent to the side edges 45 corresponding to the threaded opening 25 of the horizontal flanges 24. The access openings 48 have a smaller cross-section diameter than the head portion 36 of the leveling screws 20. Thus the head portions 36, over their circumferential portion, actually abut the undersurface of the cover plates 19 in the region annularly disposed from the access openings 48. By introducing a screw driver tip through the access openings 48 and turning the leveling screw 20, the entire subassembly (cover plates 19, spacer strips 18 and longitudinal channels 17) can be raised above the horizontal flange 24 as shown in FIGURE 3. The cover plates 19, it will be seen from FIGURE 3, actually rest upon the head portions 37 of the leveling screws 20.

From inspection of FIGURE 2, it will be seen that the entire electrical trench 10 is at or below the screed line of the concrete 14. The horizontal tongue 35 provides a shelf serving as a smooth concrete edging. There are no elements elevated above the electrical trench which might interfere with concrete pouring or leveling or which might become damaged by the passage of wheelbarrows, carts and the like thereover.

When the decorative floor covering 15 is to be applied, the fastening screws 21 are withdrawn and the cover plate 19 is removed. The spacer channels 18 are turned so that the vertical lips 39, 40 are interchanged. Now the longer vertical lip 39 is uppermost, as seen in FIGURE 3, and it extends above the upper surface of the horizontal tongue 35 by the thickness of the decorative floor covering 15. The gasket bead 42 is moved to the other one of the gasket receiving grooves 41 and the cover plates 19 are replaced. Fastener screws 21 (see FIGURE 5) having a head portion 49 corresponding to the thickness of the floor covering 15 are installed to secure the cover plates 19. Now the uppermost vertical lip 39 of the spacer strip 18 serves as a divider element which is flush with the decorative floor covering 15. The fastener screw heads 49 also are flush with the floor covering 15 for ready removal when access to the interior of the electrical trench is desired. The decorative floor covering 15 covers the access opening 48.

From inspection of FIGURES 3 and 4 it will be apparent that the depending vertical flange 30 remains in abutment with the outer edge of the horizontal flange 24 over the range of elevation of the leveling screws 20. Thereby the wet concrete 14 is prevented from entering into the interior of the present electrical trench.

According to the provisions of the patent statutes, I have explained the principle, preferred embodiment and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated an described. Y

I claim:

1. In an electrical trench for use in a building floor, said trench having generally rectangular aligned abutting cover plates substantially flush with the level of said floor, the improvement in exposed edge construction comprismg:

a longitudinal strip extended along each side of the trench substantially flush in part with the said level of the said floor, means for detachably securing said cover plate to said longitudinal strips,

a linear spacer strip interposed between and engaged with each of said longitudinal strips and said cover plate, said linear spacer strip having a Z-shaped configuration and including a flat body portion and opposed vertical lips extended from the said body portion, a first of said vertical lips being shorter than the second of said vertical lips, said spacer strip being disposed in one of two alternative positions, whereby when the said body portion is positioned with a first surface uppermost, the said first of said vertical lips extends upwardly and terminates substantially at the said level of said floor, and when the said body portion is positioned with the othersurface uppermost, said second of said vertical lips extends upwardly and terminates above the said level of said floor to serve as a floor covering divider, said cover plates being adapted to engage said spacer strips in either of the said two positions.

2. The electrical trench of claim 1 wherein said spacer strip has a gasket-receiving groove in each of its horizontal surfaces.

3. In an electrical trench, the combination comprising:

a generally U-shaped channel having a horizontal web,

a vertical leg at each end of said web and a horizontal flange at the upper end of each said vertical leg, a plurality of spaced threaded first openings in the said horizontal flange,

a longitudinal screed bar associated with each said horizontal flange, said longitudinal screed bar having a horizontal body portion, the under surface of which overlies said horizontal flange, an upper vertical flange extended from the outer end of said horizontal body portion, a lower vertical flange depending from said horizontal body portion and extending beneath the said horizontal flange, spaced openings extending through said horizontal body portion corresponding with said spaced threaded first openings, a plurality of spaced threaded second openings in said horizontal body portion,

a Z-shaped strip associated with each said longitudinal screed bar having a central portion resting upon an upper surface of the said horizontal body portion, and opposed vertical lips, one of said vertical lips being in substantial abutment with the inner face of the said horizontal body portion and the other of said vertical lips being in substantial abutment with the said upper vertical flange, one of the said vertical lips being of the same length as the said upper vertical flange and the other of the said vertical lips being longer than the said upper vertical flange, a plurality of spaced screw head openings in said central portion corresponding to the said spaced threaded first openings, a plurality of spaced openings in said central portion corresponding to the said spaced threaded second openings, said Z-shaped strip being reversible whereby either side of the said central portion may rest upon the said upper surface of the said horizontal body portion,

a generally rectangular cover plate having side edges and end edges, the said cover plate resting along its side edges upon the upper surface of the said central portion of the said Z-shaped strip with the said side edges being in substantial abutment with the upper ones of said vertical lips, a plurality of spaced ac cess openings adjacent to the said side edges of the said cover plate corresponding to the said spaced threaded first openings, a plurality of spaced screwreceiving openings in said cover plate corresponding to the said spaced threaded second openings,

fastening screws having a head portion and a threaded shaft, the said threaded shaft extending through the said screw-receiving opening of the cover plate and also through the said spaced openings of 6 the said Z-shaped strip and being further threadedly engaged in the said spaced threaded second openings, whereby the said cover plate, said Z-shaped strips and said longitudinal screed bars are secured together as a unitary sub-assembly,

leveling screws having a head portion and a threaded shaft, the said threaded shaft extending through the openings of the said horizontal body portion and being threadedly engaged in the said spaced threaded first openings, the said head portion being within one of the said screw head openings of the said Z-shaped strip beneath one of the said access openings of the said cover plate, said unitary sub-assem bly resting on a said head portion of said leveling screws above the said horizontal flanges, whereby a screw turning implement may be introduced through the said access opening to turn the said leveling screw with respect to the said threaded first opening to adjust the height of the said unitary sub-assembly with respect to the said horizontal flange.

a. The electrical trench of claim 3 wherein the said Z-shaped strip has a recess groove along each edge surface opposed to the said vertical lips, said recess groove serving as a gasket retaining means.

5. The electrical trench of claim 3 wherein the said lower vertical flange of said screed bar lies in a plane which is interior of the plane of the said upper vertical 6. In an electrical trench, the combination comprising:

a generally U-shaped channel having a horizontal web, a vertical leg at each end of said horizontal web and a horizontal flange extended from each said vertical a longitudinal strip supported above each of said horizontal flanges, leveling screws extended downwardly through clearance holes in said longitudinal strip and threadedly engaged with said horizontal flanges,

a linear divider strip detachably secured to each said longitudinal strip and having a vertical lip,

a rectangular cover plate spanning the distance between said leveling screws and secured adjacent to each of its edges to one of the said longitudinal strips, the said cover plate, said longitudinal strips and said linear divider strips comprising a unitary sub-assembly said unitary sub-assembly being supported by said leveling screws above the said horizontal flanges; means for adjusting said leveling for introducing a screw-turning implement to turn said leveling screw relative to the said horizontal flange whereby the said unitary sub-assembly may be adjusted in height above the said horizontal flange,

said linear divider strip being in engagement with the said longitudinal strip alternatively (a) with the said vertical lip above the said cover plate to serve as a floor covering divider and (b) with the said vertical lip below the said cover plate whereby the said cover plate and the upper portion of the said longitudinal strip are aligned to comprise a screed surface for the said trench.

7. The electrical trench of claim 6 wherein the said horizontal web is provided with a plurality of spaced openings which serve as inlets for electrical conduits.

8. In an electrical trench, the combination comprising:

a generally U-shaped channel having a horizontal web, a vertical leg at each end of said horizontal web and a horizontal flange extended from each said vertical a longitudinal strip supported above each of said horizontal flanges, leveling screws extended downwardly through clearance holes in said longitudinal strip and threadedly engaged with said horizontal flanges,

a linear divider strip detachably secured to each said longitudinal strip and having a vertical upward lip serving as a floor covering divider, said linear divider strip having at least a body portion secured in engagement with the said longitudinal strip,

a rectangular cover plate spanning the distance between said leveling screws and secured adjacent to each of its edges to one of the said longitudinal strips, said cover plate, said longitudinal strips and said linear divider strips comprising a unitary sub-assembly said unitary sub-assembly being supported by said leveling screws above the said horizontal flanges; said means for adjusting said leveling screw relative to the said horizontal flange whereby the said unitary sub-assembly may be adjusted in height above the said horizontal flanges.

9. The electrical trench of claim 8 assembled above a metal cellular floor wherein the said trench extends transversely of the parallel cells of the said metal cellular floor, said horizontal web is secured to the upper surface of said metal cellular floor and at least one opening is provided in the said horizontal Web and a subjacent one of the said metal cells to serve as an inlet for electrical conduits.

10. In an electrical trench for use in a building floor, the combination comprising:

a generally U-shaped channel having a horizontal web,

a vertical leg at each end of said horizontal web and a horizontal flange at the upper end of each said vertical leg,

a longitudinal strip supported above each of said horizontal flanges, leveling screws extended downwardly through clearance holes in said longitudinal strip and threadedly engaged with said horizontal flanges,

a linear divider strip above each said longitudinal strip, said linear divider strip having a body portion which has at least two flat surfaces of which at least one of said flat surfaces is in engagement with the said longitudinal strip, at least one vertical lip extending from the said body portion, said linear divider strip being detachably secured to the said longitudinal strip whereby the said vertical lip may be alternatively disposed (a) beneath the level of said floor when the said body portion is positioned with one of said surfaces in engagement with the said longitudinal strip, and (b) above the level of said floor when the said body portion is positioned with the other of said surfaces in engagement with the said longitudinal strip, whereby the said vertical lip serves as a floor covering divider when disposed above the level of said floor,

a rectangular cover plate spanning the distance between said leveling screws and secured adjacent to each of its edges to one of the said longitudinal strips, the said cover plate, said longitudinal strips and said linear divider strips comprising a unitary sub-assembly said unitary sub-assembly being supported by said leveling screws above the said horizontal flanges, means for adjusting said leveling screws relative to the said horizontal flange whereby the said unitary sub-assembly may be adjusted in height above the said horizontal flanges.

11. In an electrical trench, the combination comprising:

a generally U-shaped channel having a horizontal web, a vertical leg at each end of said horizontal web and a horizontal flange extended from each said vertical a unitary sub-assembly supported above the said generally U-shaped channel comprising:

longitudinal strips, one each above each said horizontal flange,

linear divider strips, one each detachably secured to one of said longitudinal strips and having a vertical upward lip serving as a floor covering divider, said linear divider strip having at least a body portion secured in engagement with said one of said longitudinal strips, and

a rectangular cover plate secured adjacent to each of its edges to one of the said longitudinal strips;

means for supporting the said unitary sub-assembly above the said generally U-shaped channel comprising leveling screws having a threaded portion which is threadedly engaged solely with said horizontal flanges and extended upward-1y therefrom through said longitudinal strips, said cover plate spanning the distance between the said leveling screws, the heads of said leveling screws having screw-turning means above the said longitudinal strip and below the upper surface of the said cover plate, each of said apertures in the said cover plate corresponding to each said leveling screw, said unitary sub-assembly being supported by the said leveling screws above the said horizontal flanges, means for adjusting said leveling screws relative to the said horizontal flange whereby the said unitary sub-assembly may be adjusted in height above the said horizontal flanges.

12. A closure mounting means for underfloor wiring ducts which comprises a strip having opposed side faces, opposed longitudinal edges, and a flange adjoining each said edge, one of said flanges extending angularly from and continuous to one of said side faces and the other of said flanges extending angularly from and contiguous to the other one of said side faces, each said flange being substantially coextensive in length with said strip, each said flange having a planar edge surface in substantially parallel spaced relation to the adjoining one of said side faces, one of said flange edge surfaces being spaced from the adjoining one of said side faces a greater distance than the other of said flange edge surfaces is spaced from the adjoining one of said side faces whereby one of said flanges is of greater height than the other of said flanges, and means forming a generally horizontal supporting surface for said strip, said strip having a first position on said supporting surface wherein one of said side surfaces of said strip is seated thereon and a second position on said supporting surface wherein the other of said side surfaces of said strip is seated thereon whereby in said first position said flange of lesser height projects above said supporting surface and in said second position said flange of greater height projects above said supporting surface.

13. In an underfloor wiring duct having a top opening, a horizontally disposed supporting surface defining at least in pair said top opening, a lip extending upwardly from said supporting surface, and a closure plate arranged for support on said supporting surface, closure mounting means comprising a strip having opposed side faces, opposed longitudinal edges, and a flange adjoining each said edge, one of said flanges extending angularly from and contiguous to one of said side faces and the other of said flanges extending angularly from and contiguous to the other one of said side faces, each said flange being substantially coextensive in length with said strip, each said flange having a planar edge surface in substantially parallel spaced relation to the adjoining one of said side faces, one of said flange edge surfaces being spaced from the adjoining one of said side faces a greater distance than the other of said flange edge surfaces is spaced from the adjoining one of said side faces, whereby one of said flanges is of greater height than the other of said flanges, and means forming a generally horizontal supporting surface for said strip, said strip having a first position on said supporting surface wherein one of said side surfaces of said strip is seated thereon and a second position on said supporting surface wherein the other of said side surfaces of said strip is seated thereon whereby in said first position said flange of lesser height projects above said supporting surface and in said second position said flange of greater height projects above said supporting surface.

14. A closure mounting means as defined in claim 13, said strip flange of lesser height having an edge substantially flush with the edge of said lip when one of said side faces is seated upon said supporting surface, said strip flange of greater height having an edge projecting above 9 said lip edge when the other of said side faces is seated upon said supporting surface.

15. The combination defined in claim 3 wherein the said longitudinal screed bar has a vertical web, an upper horizontal leg extending outwardly from the upper end of the said vertical web, a lower horizontal leg extended outwardly from the lower end of said vertical web, an upper vertical flange extended from the upper end of said upper horizontal leg, a dependent vertical flange depending from the outer end of said lower horizontal leg, said vertical leg being inwardly presented whereby the said lower horizontal leg overlies the said horizontal flange, the said spaced opening extending through both of said horizontal legs.

10 zontal flange extends from the upper edge of each said vertical leg.

References Cited by the Examiner UNITED STATES PATENTS 1,364,323 1/1921 Shanley 9434 2,063,569 12/1936 Walker 50127 X 2,931,533 4/1960 Wiesrnann 50-127 X FOREIGN PATENTS 471,845 1951 Canada.

LAVERNE D. GEIGER, Primary Examiner.

WILLIAM I. MUSHAKE, Examiner.

16. The combination of claim 8 wherein the said hori- 15 A. PERHAM, H. ARTIS, Assistant Examiners. 

1. IN AN ELECTRICAL TRENCH FOR USE IN A BUILDING FLOOR, SAID TRENCH HAVING GENERALLY RECTANGULAR ALIGNED ABUTTING COVER PLATES SUBSTANTIALLY FLUSH WITH THE LEVEL OF SAID FLOOR, THE IMPROVEMENT IN EXPOSED EDGE CONSTRUCTION COMPRISING: A LONGITUDINAL STRIP EXTENDED ALONG EACH SIDE OF THE TRENCH SUBSTANTIALLY FLUSH IN PART WITH THE SAID LEVEL OF THE SAID FLOOR, MEANS FOR DETACHABLY SECURING SAID COVER PLATE TO SAID LONGITUDINAL STRIPS, A LINEAR SPACER STRIP INTERPOSED BETWEEN AND ENGAGED WITH EACH OF SAID LONGITUDINAL STRIPS AND SAID COVER PLATE, SAID LINEAR SPACER STRIP HAVING A Z-SHAPED CONFIGURATION AND INCLUDING A FLAT BODY PORTION AND OPPOSED VERTICAL LIPS EXTENDED FROM THE SAID BODY PORTION, A FIRST OF SAID VERTICAL LIPS BEING SHORTER THAN THE SECOND OF SAID VERTICAL LIPS SAID SPACER STRIP BEING DISPOSED IN ONE OF TWO ALTERNATIVE POSITIONS, WHEREBY WHEN THE SAID BODY PORTION IS POSITIONED WITH A FIRST SURFACE UPPERMOST, THE SAID FIRST OF SAID VERTICAL LIPS EXTENDS UPWARDLY AND TERMINATES SUBSTANTIALLY AT THE SAID LEVEL OF SAID FLOOR, AND WHEN THE SAID BODY PORTION IS POSITIONED WITH THE OTHER SURFACE UPPERMOST, SAID SECOND OF SAID VERTICAL LIPS EXTENDS UPWARDLY AND TERMINATES ABOVE THE SAID LEVEL OF SAID FLOOR TO SERVE AS A FLOOR COVERING DIVIDER, SAID COVER PLATES BEING ADAPTED TO ENGAGE SAID SPACER STRIPS IN EITHER OF THE SAID TWO POSITIONS. 